Is it possible to include both in the 1 key/activation?
Yes, using the same TurboActivate.dat file.
Also, these programs will need to be able to run offline - I assume once an activation has taken place that the PC doesn't need to be online in the future?
It depends on how you set it up. But yes, you can make your program do that. (Use IsActivated() instead of IsGenuineEx()). And the best place o start is here: http://wyday.com/limelm/help/getting-started/